P0557
Brake Booster Pressure Sensor Circuit Low
Same as P0555 with the signal voltage below the plausible range. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: easy
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
Common causes
Ordered by how often each turns out to be the cause.
- Signal shorted to groundCommon
- Connector pins corroded - high contact resistanceLess likely
- Harness chafing through insulationLess likely
Parts involved
- Brake Booster Pressure Sensor
P0557 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.